The present invention relates generally to a manner by which to determine geographical positioning of a mobile station operable in a radio communication system, such as a cellular radio communication system. More particularly, the present invention relates to apparatus, and an associated method, that facilitates determination of the geographical positioning of the mobile station through the use of TOA (time-of-arrival) signaling. Large-bandwidth, low-energy signals are transmitted during pseudo-random time periods. Significantly-improved precision relative to conventional position-determination schemes is provided. The so-called xe2x80x98hearabilityxe2x80x99 problem associated with TOA-signaling schemes is reduced as the signals used by a mobile station in a position-determining procedure are more easily detected by the mobile station.
A communication system provides for the communication of data between separate locations. At a minimum, a sending station is positioned at a first location, and a receiving station is positioned at a second location. The sending and receiving stations are interconnected by way of a communication channel. Data that is to be communicated by the sending station is communicated upon the communication channel to the receiving station.
A wide variety of different types of communication systems have been developed and are regularly utilized to effectuate communication of information between the sending and receiving stations. A radio communication system is exemplary of a type of communication system. And, a mobile communication system is a type of radio communication system that permits communications to be effectuated by way of mobile stations. Generally, a mobile station is carriable by a user and is used by the user to communicate telephonically therethrough.
A mobile station is generally constructed to appear to a user to be operable in manners generally analogous to operation of a conventional, wireline telephonic station. That is to say, telephonic calls can be originated by the user of the mobile station by entering dialing digits associated with a called party. And, a telephonic call can be terminated at the mobile station in manners generally analogous to the manner by which a telephonic call is terminated at a conventional, wireline telephonic station.
One significant difference, however, relates to the use of a radio link with a mobile station, rather than a conventional wireline connection with a wireline station.
When, for instance, a call is originated at a conventional wireline telephonic station, the geographical position from which the call is originated is easily determinable. A simple mapping of the telephonic identity of the originating station with the location at which the originating station is installed provides an immediate indication of the geographical positioning of the originating telephonic station. Even if the user of the telephonic station is unable to identify the location from which the call is originated or communicate such indication during telephonic communications, the location of the telephonic station is readily ascertained.
In contrast, because of the inherent mobility of the mobile station, a call can be originated by way of the mobile station from any of many different locations, typically, from any location within a geographical area encompassed by the cellular communication system. The geographical positioning of the mobile station is therefore not easily determinable.
Determination of the location at which the call is originated is vitally important, for instance, in a request for emergency assistance. If a request for emergency assistance is made by way of a mobile station and the user of the mobile station is unable to indicate to emergency personnel the location from which the request for emergency assistance is made, timely delivery of emergency assistance might not be possible.
Several manners by which to determine the geographical positioning of a mobile station have been set forth. One manner is to make use of GPS (global positioning system) technologies. A GPS receiver is a global positioning system to detect TOA (time-of-arrival) signals generated by satellite-based transmitters. Signals transmitted by three separate satellites of the global positioning system are used by the GPS receiver to determine an accurate positioning of the GPS receiver. Incorporation of the circuitry of a GPS receiver into a mobile station permits the geographical positioning of the mobile station readily to be determined. One scheme, referred to as an A-GPS (Assisted-Global Positioning System) scheme utilizes GPS signals generated by the satellite-based transmitters, has been proposed for use in various terrestrial-cellular communication systems.
An analogous scheme determines the geographical positioning of the mobile station through the use of TOA signals generated by separate base stations of the network infrastructure of the cellular communication system. Through detection of the times of arrival of signals generated by separate ones of the base stations, positioned at known, fixed-site locations, the geographical positioning of the mobile station is analogously also determinable. One scheme, referred to as an E-OTD (Enhanced-Observed Time Difference) scheme, utilizes signals generated by three separate base transceiver stations to determine the geographical positioning of a mobile station.
Problems, however, are associated with existing A-GPS and E-EOTD schemes by which to determine the geographical positioning of a mobile station.
The precision of the position determination is lacking. That is to say, the geographical positioning cannot note the position of the mobile station with a required degree of precision to permit, for instance, emergency personnel properly to respond to a request.
And, such schemes suffer from a so-called xe2x80x98hearabilityxe2x80x99 problem.
Detection of different TOA signals to make determination of the geographical positioning of the mobile station is somewhat problematic. A signal generated by a serving base station, however, might well mask currently-generated, co-channel radio signals, including signals generated by other base stations. If signals generated by the other base stations cannot adequately be detected due to the characteristics of the signal generated by the serving base station, geographical positioning determination cannot accurately be made.
A manner is therefore needed by which better to provide for the determination of geographical positioning of a mobile station operable in a radio communication system.
It is in light of this background information related to the determination of geographical positioning of a mobile station that the significant improvements of the present invention have evolved.
The present invention, accordingly, advantageously provides apparatus, and an associated method, by which to determine the geographical positioning of a mobile station operable in a radio communication system, such as a cellular radio communication system.
Through operation of an embodiment of the present invention, geographical positioning determination of the geographical positioning of the mobile station utilizing TOA signaling is facilitated.
In one aspect of the present invention, large-bandwidth, low-energy signals are transmitted during pseudo-random time periods. The so-called xe2x80x98hearabilityxe2x80x99 problem conventionally associated with TOA-signaling schemes is reduced as the signals used by a mobile station in a geographical positioning procedure are more easily detected by the mobile station. And, the precision of the position determination is significantly improved. Position-determination precision can be on the order of centimeters instead of, e.g., only dozens of meters permitted utilizing conventional schemes.
In another aspect of the present invention, the large-bandwidth, low-energy signals are generated upon channels, such as pilot channels defined in a CDMA system, together with signals, such as pilot signals, that are continuously broadcast. The large-bandwidth signals generated at individual ones of the base stations are each broadcast during separate, pseudo-random time periods to reduce the possibility of overlap. That is to say, the large-bandwidth signals generated by different ones of the base stations of at least a set of the base stations are generated during non-overlapping time periods. The pseudo-random selection of the time periods during which the large-bandwidth signals are generated reduce the possibility of overlapping signal generation by separate ones of the base stations. The large-bandwidth signals are generated, for instance, upon a common pilot channel defined in a W-CDMA (wideband, code-division, multiple-access) network or upon a broadcast channel in a TDMA (time-division, multiple-access) network. By generating such large-bandwidth signals, such signals make co-channel interference on the pilot channel appear to be a narrow band interferer. Subsequent correlation operations performed at the mobile station, only the large-bandwidth signal contributes, in a significant manner, to resultant correlation results. Correlation calculations are performed and are used to determine the time-of-arrival of a signal at the mobile station. The time-of-arrival of the signal, in one implementation, is determined to be the time at which a peak value of correlation determined by the correlation calculation is made. Suppression of pilot channel signals and receiver noise through the correlation function assist in improvements in the quality of the time-of-arrival determinations.
In another aspect of the present invention, insertion of a large-bandwidth, e.g., 2 GHz, signal is intermittently injected into the channel. Detection of the signal, and subsequent operations performed thereon, permit the accuracy of geographical positioning determinations to be increased. Also, use of such large-bandwidth signals increases the possibility that a mobile station shall be able to detect the signals generated by enough base stations to permit the geographical positioning of the mobile station.
Implemented in an otherwise-existing CDMA or TDMA (or other) communication system, new apparatus is provided for the network part of the system. The new apparatus causes the generation of the large-bandwidth, low-energy signal for broadcast upon the a channel to which the mobile station tunes. Pseudo-random transmission time periods are determined to reduce the possibility of concurrent transmission of the large-bandwidth signals upon the pilot channel. And, because the signal energy level of the signals is of a low value, i.e., beneath the noise floor of the channel, the interference-causing characteristics of such signals are minimal.
Apparatus is also provided for the mobile station, or elsewhere, to determine the geographical positioning of the mobile station. Detection is made at the mobile station of the large-bandwidth signals. Correlation operations are performed upon the detected signal energy, and the times of arrival of the large-bandwidth signals. A position determination is made through solution of a set of non-linear equations that are functionally dependent upon measured time differences, together with known coordinates of the base stations from which the signals are broadcast, together with their times of transmission.
In these and other aspects, therefore, apparatus, and an associated method, is provided for a radio communication system operable to communicate communication signals upon a common bandwidth. The radio communication system has a network part installed to encompass a geographical area and a mobile station positionable therein. Determination of geographical positioning of the mobile station is facilitated. At least a first wideband signal generator generates at least a first wideband signal upon at least a first channel. The first channel is allocated to at least a first network station upon which to transmit a first signal. The first wideband signal is generated during first pseudo-random time periods, together with the first signal. The first wideband signal is of a bandwidth greater than a corresponding first-signal bandwidth of the first signal, and the first wideband signal is of a signal level less than a corresponding first-signal signal strength.